With various electronic devices being widely used, higher requirement is proposed on operative stability of the electronic devices.
Many electronic devices have a rated current for operation, if an operating current of the electronic device at present exceeds the rated current, it would cause the electronic device to stop operation and even to be damaged.
In prior art, in order to lower a loss resulted from that the operating current exceeds the rated current, an over-current protection module is general provided at an output terminal of a switch power supply of an electronic device. When an output current of the switch power supply exceeds the rated current, the over-current protection module starts an over-current protection function, i.e. automatically turns off the power supply by means of circuit characteristics thereof, so as to avoid exceeding current from flowing into other operating circuits of the electronic device, which will damage the circuit and yield loss. Therefore, a current which is slightly higher than the rated current and just able to start the over-current protection function of the over-current protection module is a target current for over-current protection of each electronic device.
The target current for over-current protection of the each electronic device corresponds to one over-current protection point of a resistance of the over-current protection module of said electronic device. Therefore, for each electronic device, when an operating current of the electronic device exceeds or is equal to the target current for over-current protection, the over-current protection module is actuated to start by adjusting a resistance of a resistor in the over-current protection module, so as to function as protecting the electronic device.
For an example described here, the electronic device is a switch power supply. During manufacturing process of the switch power supply in prior art, a variable resistor VR is generally provided in the over-current protection module of the switch power supply, for manually adjusting the resistance of the resistor. In a producing line, the over-current protection (OCP) point of the electronic device is actuated by adjusting the resistance value of the variable resistor VR, and the OCP point which has been set is secured by applying glue to the variable resistor VR.
FIG. 1 is a flow chart diagram illustrating a conventional method for setting an over-current protection point of an electronic device, which comprises:
step S1: setting a target current for over-current protection for a direct-current electronic load;
step S2: connecting a switch power supply which is not assembled with a housing to the electronic load and keeping an electronic supply from the switch power supply to the electronic load with a current equal to the target current for over-current protection;
step S3: continuously turning the resistance variable resistor VR in the over-current protection module of the switch power supply until the resistance reaches an OCP actuation point, where the operation current exceeds the target current for over-current protection, so that the over-current protection module is actuated to perform over-current protection, so as to cutoff the electronic supply from the switch power supply to the electronic load;
step S4: applying a fixing glue to the resistance variable resistor VR to fix the resistance of the resistance variable resistor VR at the currently actuated OCP point, so as to prevent the resistance of the variable resistor VR from changing.
However, each of the above steps is performed manually, which slows operating speed and seriously blocks promotion of productivity. At the same time, it is difficult for manual operation to assure higher correctness, because it is easily to manually change the resistance of the variable resistor VR. Moreover, since the fixing glue may shrink during cooling and may expand during heating, it is easily to have the secured resistance of the variable resistor VR displaced and offset from the OCP point which has been set, seriously affecting the quality of the electronic device.